I am quite confident that the rule was "who gets the most money after 10 rounds". Technically if you don't cash out - you didn't GET the money. Hence the MC cashing out early - before the exchange died - is in fact the winning move. But a technicality isn't enough to win - however making the opponent lose every single ally he has - including the group he was representing - is enough to win the war - even if formalities are disregarded.